The Lewises of Harpton were a branch of the Lewises of Gladestry. It was Thomas Lewis’s father Hugh who founded the family fortunes, entering public life in a modest way about 1536 under Devereux patronage, speculating in land at the time of the dissolution of the monasteries, and in 1563 taking extensive leases of crown lands. Hugh left Gladestry in the occupation of a junior branch of the family, and moved to Harpton, some four miles to the north. Lewis himself inherited these estates and renewed the leases on succeeding his father. He had already added to them some former chantry lands in New Radnor as well as the site of Old Radnor (devastated in 1401), which he bought from New Radnor corporation in 1565 or 1566. He was one of the original burgesses of New Radnor under the charter of 1562 and probably also bailiff there. In his capacity of collector of subsidies he was accused in the Exchequer of withholding money from the ‘high collector’, and in 1564 Bishop Scory of Hereford reported to the Privy Council that, in company with the neighbouring magistrates, Lewis was ‘but a neuter’ in religion.
When Lewis stood for the county in 1572 he was successfully challenged by Roger Vaughan of Clyro through the gerrymandering (as Lewis alleged in the subsequent Star Chamber suit) of the sheriff, Vaughan’s kinsman Edward Price.
Lewis made his will 15 June 1601, ‘being somewhat diseased in body, yet, God be praised, of sound and perfect memory’. He remembered the poor of his parish and made bequests to his sons; the residue went to his eldest son Hugh, whom he appointed sole executor. The will was proved 12 May 1607.